A circuit breaker, comprising a jet (9), an active side first connection member (13), an active side second connection member (14), an insulating connection member (10), an arc extinguishing chamber mounting frame (11), an insulating pull rod (7), and a protective plate (8) disposed on the arc extinguishing chamber mounting frame (11) and used for isolating an insulating section of the insulating pull rod (7) from an inner cavity of an arc extinguishing chamber (4). Both ends of the insulating connection member (10) are connected to the active side first connection member (13) and the active side second connection member (14), respectively. The insulating connection member (10) is provided with a cavity in the shape of a through hole where the jet (9) is mounted. The jet (9) and the insulating connection member (10) are limited and coaxially fixed by means of the active side first connection member (13) and the active side second connection member (14). An end portion of the protective plate (8) slidably matches a side wall of the insulating pull rod (7). The service life of the circuit breaker is prolonged.